With the development of storage technology, the solid state disk (SSD) has been widely used. Compared with the traditional hard disk drive (HDD), SSD has advantages such as fast speed and low power consumption. Generally, a HDD storage system uses a SSD with hundreds of GBs or TBs as its cache space to store frequently accessed hot data in order to accelerate data access of HDD storage system.
The lifecycle of the SSD is greatly impacted by writing operation, which is different from HDD. Too many writing operations would render the SSD unreliable. Thus, the number of writing operations that can be performed by a SSD flash disk is limited and varies according to the type of SSD. For example, the number of writing operations that can be performed by multi-level cell (MLC) is only a tenth of that of a single-level cell (SLC), while the number of writing operations that can be performed by a three-level cell (TLC) is only a tenth of that of the MLC. Furthermore, the lifecycle of the SSD is affected by disk temperature and working current of the SSD. When the temperature or working current is high, the wearing extent of SSD will be great, thereby causing more SSD data blocks to break down.
In some cases, some disks will cause serious wearing due to a large number of writing operations such that the overall performance of SSD cache deteriorates, thereby rendering SSD cache instable or inaccessible. The traditional storage system would generally slow down wearing speed of the SSD disk by limiting the frequency of accessing SSD. However, since the frequency of accessing the storage system is reduced, the overall performance of the storage system would also deteriorate correspondingly.